"My life's an open book," people might say. "I've got nothing to hide." But now the government has large dossiers of everyone's activities, interests, reading habits, finances, and health. What if the government leaks the information to the public? What if the government mistakenly determines that based on your pattern of activities, you're likely to engage in a criminal act? What if it denies you the right to fly? What if the government thinks your financial transactions look odd—even if you've done nothing wrong—and freezes your accounts? What if the government doesn't protect your information with adequate security, and an identity thief obtains it and uses it to defraud you? Even if you have nothing to hide, the government can cause you a lot of harm.
In the above passage from the book Nothing to Hide, Daniel J. Solove extrapolates on what could happen if everybody simply accepted the notion that the benefits of government surveillance outweigh the disadvantages. Many people forget that they do have something(s) to hide, and so surveillance is harmful to them rather than helpful. With the help of PGP, Tor, OTR, GNU/Linux, and other encryption/anonymity tools, one can use the internet with a very low probability of being spied on.